1. Field of the Invention
The present invention relates generally to magnetic disk drive apparatus and more particularly to an improved disk drive and centering mechanism for use in microfloppy disk drives.
2. Background of the Present Invention
Microfloppy disk drives of the type in which the present invention has particular application are disclosed in U.S. Pat. No. 4,581,669 (which corresponds to U.K. Patent Application GB-2082371A published Mar. 3, 1982); such patent is hereby incorporated by reference. Prior art drives of the type disclosed therein include a driving mechanism for engaging and rotating the magnetic disk contained in a microfloppy cassette. Such mechanism includes a means for centering the media within the cassette envelope so that it is free to properly rotate therewithin. Whereas initial engagement between the drive spindle and media hub is by attractive force exerted by small magnets located in the spindle hub, centering of the media and operational drive thereof is accomplished by means of an offset drive pin or roller mounted on a flexure which penetrates and acts on one side of an eccentrically positioned rectangular slot formed in the media hub. The pin and flexure are configured such that there is interference between the pin and the rectangular slot in the media hub so that during engagement,one side of the central opening in the media hub is moved into contact with and then held in firm contact with one side of the spindle shaft. In existing drive pin designs, the drive pin is supported in cantilever fashion by the flexure and tends to tilt slightly both when it is engaged and depressed by the media hub. and when it is used to drive the hub. This tilting is likely to cause pin misengagement or disk miscentering and in some cases may result in disengagement between the drive spindle and the media hub.